Microelectromechanical systems (MEMS) is the technology of very small devices, typically within a size range of about 1 μm to 1 mm. MEMS devices are produced with semiconductor fabrication technology. There are currently many types of MEMS devices used in many different applications, for example, microphones, pressure sensors, and mechanical resonators.
One common type of MEMS device is a BAW (Bulk Acoustic Wave) filter. BAW filters are electromechanical devices that can be implemented as ladder or lattice filters. BAW filters typically operate at frequencies from around 2 to around 16 GHz, and may be smaller or thinner than equivalent SAW filters. The two main variants of BAW filters are Thin Film Bulk Acoustic Resonator or FBAR and Solid Mounted Bulk Acoustic Resonator or SMR. BAW filters are frequently used in wireless applications. Various methods of designing and making BAW filters are known in the art. BAW filters are typically implemented at the “wafer level.” Identical BAW structures are formed on a large semiconductor substrate (wafer) that is subsequently cut (singulated) into identical separate dies (dice).